This invention relates to a gas-insulated switchgear, and more particularly to a shortened gas-insulated switchgear of 11/2(one-and-half) circuit breaker system.
A prior art, three-phase common tank type gas--insulated switchgear of 11/2 (one-and-half) circuit breaker system is disclosed in, for example, Japanese Utility Model Unexamined Publication No. 139307/81. In the disclosed gas-insulated switchgear, three circuit breakers are connected between a pair of main bus bars in such a relation that adjacent circuit breakers are connected to a connecting bus bar at their nearest lead-out parts, and disconnecting switches and earthing switches are provided on this connecting bus bar. This 11/2=(3/2) circuit breaker system refers to a breaker system in which three circuit breakers are connected between two main bus bars.
FIG. 1 is a partly cut-away, schematic front elevation view of such a prior art, gas-insulated switchgear of 11/2 circuit breaker system.
Referring to FIG. 1, a pair of main bus bars 1 and 2 are disposed in a relation spaced apart by a predetermined distance, and one set of three circuit breakers 3, 4 and 5 are disposed in tandem to be connected between the two main bus bars 1 and 2. Each of the circuit breakers 3, 4 and 5 is formed with a pair of lead-out parts at its axial ends respectively, and these lead-out parts are connected to connect the three circuit breakers 3, 4 and 5 in series between the main bus bars 1 and 2. The circuit breaker 3 is connected to its lead-out part 3a, nearer to the main bus bar 1 than the lead-out part 3b, to the main bus bar 1 by a connecting bus bar 6. Also, the circuit breaker 5 is connected to its lead-out part 5b, nearer to the main bus bar 2 than the lead-out part 5a, to the main bus bar 2 by a connecting bus bar 7.
The connection between the three circuit breakers 3, 4 and 5 is such that adjacent circuit breakers are connected to their lead-out parts nearer to each other. That is, the circuit breakers 3 and 4 are connected to their nearer lead-out parts 3b and 4a by a connecting bus bar 8, and the circuit breakers 4 and 5 are connected to their nearer lead-out parts 4b and 5a by a connecting bus bar 9. Further, external lead-out means 10 and 11 such as bushings, gas bus bars or cable heads for connection to an external equipment are connected to substantially middle portions of the connecting bus bars 8 and 9 repectively.
However, due to the necessity for provision of disconnecting switches and earthing switches on the connecting bus bars 8 and 9, these connecting bus bars 8 and 9 require a large axial length, and, as a result, the distance d between the circuit breakers 3, 4 and 5 increases inevitably as seen in FIG. 1. Therefore, the prior art gas-insulated switchgear has been defective in that the overall size of the switchgear becomes large and bulky inevitably.